Can i ask an honest question without getting flamed (im actually fine with being flamed), or banned, or whatever?

Whats the deal with quench here?

It seems every single post that has anything remotely to do with compression ratios, theres more than a few guys on here that are fascinated with "Quench"
Most actual engine builders call it "Squish" Which is only slightly less dumb sounding than Quench.
I will use "Quench" for everyone that loves that word, but when you read it please remember i prefer Squish.

Quench is a misnomer, because the whole idea of the quench area is not to "quench" the new beginings of the combustion process, it is to give it a head start. Everyone here obviously knows what comes next, as most of you have studied the 1/8th paragraph in Smokey Yunicks 200 page book where he breezes over it. And at the end of that small paragraph it reads (Quoting offhand, but you will get the idea) Quench/squish while important, is not THAT important, as long as it is not excessive one way or the other.

How did the magical unwarrenteed HEMI that blew up all the time, so they didnt give it a warranty, even run with zero quench?
How did honda make 250 plus HP out of the S2000 with, you guessed it, little to zero quench.
*Most* Dodge 340/360/440 Engines had like .100-.125 Quench. Im not kidding. They were so poorly machined and slapped together it was common to find pistons .040 and .050 in the hole, and a dished piston, and a dished head!. Any old guys remember the quench step piston? Ya, it didnt work so great. Twas still a stone.

Heres 2 engines, that would actually benifit huge from tightening up the quench, Flathead Fords and a Briggs and Stratton.

Quench, in racing engines is used to lower detonation. It can cool the piston. It can do alot of great things.
Under sustained WOT at high operating temperatures.
In your street car. Not so much. Idle around town, take it to 6000 6500 (woooo) once a week...

Quench is almost insignifigant in street engines, it is not even worth looking at 99% of the time.
And never mind you deck the block, buy a flat top, and run a performance type gasket, i can guarentee that thing is between .050 and .040 quench. You didnt just launch a nasa missle or finally reengineer the wheel, you decked the block a got a decent piston, and somehow you engineered your quench?

Now heres the kicker: Have any of you, even once, though about rod stretch when calculating your critical, cannot deviate, must have "quench"? Theres one guy going, "Ya i have!"
You my friend, are the smartest man on this site! The rest are going "Oh man, my quench is .0xx (depending on profile and material used) tighter when my cars actually moving down the street, my dreams have been smashed!

As for real performance/racing applications, if you are doing your homework, your going to depth mike the block/piston at preassembly to get your in the hole number. THEN you calculate in rod stretch, and bearing material, and oil film compression, and then you find out your actual gotta have quench number, after of course taking into the account that different kinds of pistons do grow at different rates when they are absorbing all the combustion heat, and that they dont just grow in diameter. Then you machine the block, AFTER adding everything up.

Now i see you guys arguing over .005 in quench.....
Now we take into account that your piston grew .002 up, at 6000 your rod has streched, for arguments sake, .005, you used a digital caliper instead of a $500 depth mike, you probably didnt measure TDC and piston rock correctly with a accurate gauge and a 24 inch degree wheel, you are probably at least .010 out on your static measurements!

And you all are telling me and everyone else on here how critical quench is, and how to check it?

PLEASE, keep it realistic fellas! Anyone can use Google and look like a genius. Anyone can memorize a Yunick, or how to build a small block chevy book (which are both outdated by 20+ years now, things have changed a bit in racing engines in 20 years)

All the new guys on here, are all wound up about quench, and swirl port heads, and pushrod length, and all sorts of crap that only really matters if you race your engine. Stick to the basics. Stop being so holier than thou with each other. Try and help someone get into the hobby, instead of confusing them with wild calculations and theory. Small block chevs have made up to 365HP with all of the stuff you guys call junk. Soft exhaust seats, "too wide" "too narrow" lobe centers, small valve springs, short dual plane intakes, with exhaust manifolds!!
Then i see posts where the guys got a stone asking about something stupid like coil bind with his 480 lift 116 centerline turd cam, that might make 250 hp and you all are desktop dynoing it at 344 hp, and "you gotta use an airgap intake with a port match precisly 2 inches into the head with vortecs and 1 5/8 headers ONLY, and a .037 quench and you gotta use plasma moly rings with a 800 finish on the cyls with a burnishing brush run at 400 rpm, and a 625 edelbrock with A5 metering jets......."

We talk about pushrod length for hundreds of pages, and then most of you are running stock rockers or chinese summit rockers that are deflecting all over the place, why??
Do you have a jesel state of the art rigid valve train to warrant .117 longer custom pushrods? or will .125 do if you are using a 510 hydraulic piece of junk with lifters that compress .020 and blow all of the measurements and hours of theory out the window???

Sorry about the rant. It went longer than i expected, I couldnt take it anymore. If I dont get banned, i will try to help more, in practical ways without all the big word voodoo i see so much.

mouse? not sure who you are talking about? Ive seen a few members mention quench/squish, but not to the detail you mentioned. Different combustion shapes promote different flame propagation rates and the fuel itself could be broken down a lot also,,,,,I dont see the harm in mentioning certain ideas and certainly friendly debates and discussions are beneficial.
I hope you throw in your 2 cents worth more often. I certainly dont agree with everyone and I still really enjoy the site.
Thanks for the great post

Must be nice to be so much smarter than the guys that have been building and hotrodding much
longer than you've been alive.

I'll never understand this ^^^ thinking..
look around, at any racing discipline. and look at the ones that are in the engine rooms.. building power that most could only dream of..
not many 60+ y/o in the room..
in fact they are the ones that tend say. it can't be done..
most said we'd never see speeds like bill eliots t-bird at superspeedways again because of the restrictor plate.. guess they where wrong..

yes guys that have been going for 30+ years have allot of good info in their gray matter..
but guys that have been learning from age 10 and are under 35 are running circles around the old pro's
so I can't see where this always comes up.. that younger means not as smart or smarter..

I think mouses post was a good one.. and pointed to things that some that ask about their build might never even think of. and most times don't have to..

cause deburing and rounding of the sharp edges of the valve releafs and spark plug threads, and anyother sharp points in the piston or champer. will do more to "quench" pre ignition than any "quench pad" measurement

Lets say for argument's sake that quench does nothing for performance or emissions or economy or to help prevent detonation.

When talking about the compression ratio of an engine, if a quench figure isn’t specified, then all the parameters would need to be listed individually.

An example would be saying the CR was based on a 0.040” quench, OR it would need to be stated that the CR is based on what the piston to deck measurement is, what the compressed head gasket thickness is, what the deck height of the block is, and what the compression height of the piston is along with what the chamber and dish/dome volume is.

So it is easy to see how using a quench figure that encompasses ALL the measurements (except the combustion chamber and piston dish/dome volume) is much simpler than listing each measurement individually.

BTW, the 0.040" quench figure is used because it's generally viewed as being optimum for a steel rod street/strip engine using a wedge combustion chamber. If the actual quench measurement in question is other than 0.040”, the difference in the CR can be easily found using a compression ratio calculator.

The same principals apply to proper valve train geometry. Sure- the engine will run most times using stock length pushrods. But is it somehow wrong to set the valvetrain up correctly? It doesn't cost any more for the right length p-rod than it does the wrong length p-rod, so what's the problem?

As far as "guys arguing over .005 in quench", "swirl port heads" and "talk about pushrod length for hundreds of pages", I'll chalk that up to hyperbole and maybe too much caffeine.

As to "I will use "Quench" for everyone that loves that word, but when you read it please remember i prefer Squish", squish and quench are two entirely different phenomena. So if you're going to preach at least get the terminology right. "Quench" is used for expedience only. Again, see Quench for more on the subject of quench and what it all really means.

But what you will not see me do is dumb anything down to make it more palatable for those too lazy or uncommitted to do the best job they can.

Last edited by cobalt327; 11-22-2012 at 07:14 AM.

The Following 4 Users Say Thank You to cobalt327 For This Useful Post:

...cause deburing and rounding of the sharp edges of the valve releafs and spark plug threads, and anyother sharp points in the piston or champer. will do more to "quench" pre ignition than any "quench pad" measurement

Pre ignition and detonation are two different things w/different causes and cures.

I worry sometimes that we cause young people to stay on the porch because they can't afford or don't understand how to do things exactly right. Numbers matter when people are trying to legislate our hobby out of existence. On the technial side those factory motors with mega "quench" either burned leaded fuel or had extremely low compression or both. The goal is 0 quench the static clearence considers all the factors that you say we ignore.

I'll never understand this ^^^ thinking.....guys that have been learning from age 10 and are under 35 are running circles around the old pro's
so I can't see where this always comes up.. that younger means not as smart or smarter..

You don't think the majority of us have been learning from age 10 to way past your magical age of 35? Think before you post statements like that, some day you might gain a lot of this knowledge we "old pros" have.

I wonder why some hide their age in their profiles.

__________________
Boost adds dignity to what would otherwise be a vulgar brawl...

You don't think the majority of us have been learning from age 10 to way past your magical age of 35? Think before you post statements like that, some day you might gain a lot of this knowledge we "old pros" have.

I wonder why some hide their age in their profiles.

wasn't a magical age, if you look at the post I quoted from..
and the post he qouted.. from you'd see why..

I don't see why some think because they are older they are somehow smarter than someone else..(and if you read the post I quoted from and that whole post you'd have got that)

my next engines a 454 based 489 that will need a DOME to get any compression..
so a "quench pad" area should be a great thread..

Quench/squish really got attention when emissions standards got tighter. Complete burn and not sending any unburned hydrocarbons out the exhaust became important, and quench considerations were part of making that possible. Find an engineer that was working in OEM engine design in the 1980's if you want to know more.

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